Question

An unequal angle ISA $80\text{mm}\times 50\text{mm}\times 8\text{mm}$ is welded to 12 mm thick gusset plate at site as shown in figure. The angle to transmit a factored load of 120 kN. The length of weld $l_1$ and $l_2$ required are respectively.

• A. 45 mm, 65 mm
• B. 68 mm, 114 mm
• C. 60 mm, 90 mm
• D. 70 mm, 105 mm

Answer 1

The correct option is B 68 mm, 114 mm

The force to be resisted by lower side of angle

$P_1=\frac{P\times (80-30)}{80}=\frac{5}{8}\times 120=75kN$

$\therefore$ Force to be resisted by upper side of angle
$P_2=120-75=45kN$

Strength of weld per mm length $t_t=\frac{f_u}{\sqrt{3}{\gamma }_{mw}}$

$=(0.7\times 6)\times \frac{410}{\sqrt{3}\times 1.5}$
$=662.8N/mm$

$\therefore l_1=\frac{45\times {10}^3}{662.8}mm=67.8\approx 68mm$

$l_2=\frac{75\times {10}^3}{662.8}mm=113.2\approx 114mm$